IDNLearn.com: Your trusted source for finding accurate answers. Get thorough and trustworthy answers to your queries from our extensive network of knowledgeable professionals.
Answer:
Rift valleys are Formed from either from the action of tensional forces in the crust or from the action of compressional forces!
And they move due to the force of gravity!
The block mountain (horst) is left standing higher above the sunken graben!